In an anesthesia operation, an anesthetic machine is an important apparatus with which an anesthetist makes a patient to be in narcosis, so as to treat the patient. An anesthetic loop is an important device indispensable for an anesthetic machine to achieve cycle closed anesthesia. In the case that the anesthetic loop is ventilated manually, if the pressure is too high in the loop, it causes the pressure in a patient's lung to be too high, harming the patient to a certain extent, but if the pressure is too low, it can not meet the requirement of supplying air. Also, the applied pressure is different depending on different situations and if the pressure in the air path is constant, it can not meet the requirement of varying pressure. A pressure control valve is provided on the anesthetic loop, for limiting and positioning a pressure value.
During realizing the present invention, the present inventor found that the existing pressure control valve was not enough to limit and position the pressure value accurately.